如何检测android片段中按下后退按钮的时间? [英] How to detect when back button pressed in fragment android?
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问题描述
我有一个带有片段的导航抽屉项目,其中有5个菜单,问题是当我转到菜单4时,我按了后退按钮,应用程序关闭了,但是我需要将应用程序返回到第一个菜单,即所有菜单片段中.
I have project with navigation drawer with fragment, with 5 menu, the problem is when i go to menu 4 and the i press the back button the app closed, but i need the app back to first menu which is all the menu in fragment.
这是主要活动(导航抽屉)的代码
This is code for Main Activity (Navigation Drawer)
public class MainActivity extends AppCompatActivity{
DrawerLayout mDrawerLayout;
NavigationView mNavigationView;
FragmentManager mFragmentManager;
FragmentTransaction mFragmentTransaction;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/**
*Setup the DrawerLayout and NavigationView
*/
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
mNavigationView = (NavigationView) findViewById(R.id.shitstuff) ;
/**
* Lets inflate the very first fragment
* Here , we are inflating the TabFragment as the first Fragment
*/
mFragmentManager = getSupportFragmentManager();
mFragmentTransaction = mFragmentManager.beginTransaction();
mFragmentTransaction.replace(R.id.containerView,new Recommendation()).commit();
/**
* Setup click events on the Navigation View Items.
*/
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
mDrawerLayout.closeDrawers();
if (menuItem.getItemId() == R.id.nav_item_lux_level_recomen) {
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.containerView,new Recommendation()).commit();
}
if (menuItem.getItemId() == R.id.nav_item_room_index_calc) {
FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
xfragmentTransaction.replace(R.id.containerView,new RoomIndex()).commit();
}
if (menuItem.getItemId() == R.id.nav_item_utilization_factor_calc) {
FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
xfragmentTransaction.replace(R.id.containerView,new UtilizationFactorCalculator()).commit();
}
if (menuItem.getItemId() == R.id.nav_item_conversions) {
FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
xfragmentTransaction.replace(R.id.containerView,new Conversion()).commit();
}
if (menuItem.getItemId() == R.id.nav_item_lux) {
FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
xfragmentTransaction.replace(R.id.containerView,new LuxSensor()).commit();
}
return false;
}
});
/**
* Setup Drawer Toggle of the Toolbar
*/
android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this,mDrawerLayout, toolbar,R.string.app_name,
R.string.app_name);
mDrawerLayout.setDrawerListener(mDrawerToggle);
mDrawerToggle.syncState();
}
此菜单之一(片段)
public class LuxSensor extends Fragment {
TextView textLIGHT_available, textLIGHT_reading;
FragmentManager mFragmentManager;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View x = inflater.inflate(R.layout.lux_sensor,null);
textLIGHT_reading
= (TextView)x.findViewById(R.id.LIGHT_reading);
SensorManager mySensorManager = (SensorManager)getActivity().getSystemService(Context.SENSOR_SERVICE);
Sensor LightSensor = mySensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
if(LightSensor != null){
mySensorManager.registerListener(
LightSensorListener,
LightSensor,
SensorManager.SENSOR_DELAY_NORMAL);
}else{
textLIGHT_available.setText("Sensor.TYPE_LIGHT NOT Available");
}
FragmentManager fm = getFragmentManager();
return x;
}
private final SensorEventListener LightSensorListener
= new SensorEventListener(){
@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
// TODO Auto-generated method stub
}
@Override
public void onSensorChanged(SensorEvent event) {
if(event.sensor.getType() == Sensor.TYPE_LIGHT){
textLIGHT_reading.setText(event.values[0]+" LUX");
}
}
};
}
我已经尝试了互联网解决方案,但仍然关闭
I have tried solution in internet but it still closed
推荐答案
在您的MainActivity中
In your MainActivity
@Override
public void onBackPressed()
{
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.containerView,new Recommendation()).commit();
}
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